As you are probably aware certain Game Modes are unplayable because there are no Players (at least on PC).
Now besides the obvious solution to attract more Players there is a Temp Fix: Bot Servers.
There are already pretty good working Bots in Private Matches.
All you have to do is make some Bot Game Playlist(s) with the lesser played Game Modes so we can play anything else than Deathmatch and still Level Up/get Depot Points.
You could make it so that you only earn half the Experience in these Playlists and can not Prestige so there is a Limit to Bot Play.
But with that Solution we can at least earn Depot Points besides playing only TDM or paying for it.
Btw you could kindly spread that Word to your colleagues from Infinite Warfare and BO3 wich could also use that Feature.
So in the Future when inevitably those Games will have almost no Players we can still earn the (stupid) Supply Drops without purchasing COD Points.
Sorry for my Bad english btw.
I hope my Message still comes across.